The Radiation Medicine Shared Resource provides the opportunity for UCSD Cancer Center investigators to pursue an interactive approach to the determination of intrinsic radiation sensitivity. The conduct of radiation assays quantifying radiation sensitivity to ionizing radiation in vitro, as well as mathematical modeling of survival parameters, is the cornerstone of services provided. As a corollary to this purpose, the Facility lends expertise to researchers studying the cell cycle control of DNA damage and genomic instability induced by ionizing radiation both in vitro and in vivo. Services include: 1. Irradiation of Cells, Cell Lines, and Feeder Cells; Clonogenic Radiation Survival Studies. Cell strains and cell lines are irradiated with a variety of radiation fraction sizes, for single fraction experiments, and at a variety of infraction intervals, for multiple fraction experiments. Similarly, cells are irradiated at high dose per fraction for experiments requiring lethally irradiated feeder cells. Nearby Resource cell culture and incubator equipment provide for relative ease of conducting combined radiation sensitization/protection, chemosensitivity, and gene therapy approaches. 2. Whole or Partial Body Irradiation of Mice or Rats. Whole body irradiation of mouse or rat species are irradiated for a variety of purposes ranging from single fraction whole body irradiation for immunosuppression to fractionated tumor control, tumor induction, or normal body irradiation for immunosuppression to fractionated tumor control, tumor induction, or normal tissue tolerance studies. For experimental protocols requiring the irradiation of specific body regions, custom lead shielding has been tailored to the treatment volume while sparing nearby normal tissues. 3. Assistance with Radiobiologic Data Interpretation, Survival Modeling, and Illustration. Recommendations on the optimal method of interpreting radiation cell survival data allow investigators familiarity with multiple cell survival models and the derivation of interrelated radiation cell survival parameters to be used in subsequent statistical analysis.